Fix bug in PathDifference that truncated paths. (epot_tools)

trychange.py

 #!/usr/bin/python
 # Copyright (c) 2009 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 """Client-side script to send a try job to the try server. It communicates to
 the try server by either writting to a svn repository or by directly connecting
 to the server by HTTP.
 """
 
 
@@ skipping 48 matching lines @@
 
 class NoTryServerAccess(Exception):
   def __str__(self):
     return self.args[0] + '\n' + HELP_STRING
 
 
 def PathDifference(root, subpath):
   """Returns the difference subpath minus root."""
   if subpath.find(root) != 0:
     return None
-  # The + 1 is for the trailing / or \.
-  return subpath[len(root) + len(os.sep):]
+  # If the root does not have a trailing \ or /, we add it so the returned path
+  # starts immediately after the seperator regardless of whether it is provided.
+  if not root.endswith(os.sep):
+    root += os.sep
+  return subpath[len(root):]
 
 
 def GetSourceRoot():
   """Returns the absolute directory one level up from the repository root."""
   return os.path.abspath(os.path.join(gcl.GetRepositoryRoot(), '..'))
 
 
 def ExecuteTryServerScript():
   """Locates the tryserver script, executes it and returns its dictionary.
 
@@ skipping 417 matching lines @@
     if patch_name == 'Unnamed':
       print "Note: use --name NAME to change the try's name."
   except (InvalidScript, NoTryServerAccess), e:
     if swallow_exception:
       return
     print e
 
 
 if __name__ == "__main__":
   TryChange(None, None, False)